Field of Invention
The present invention relates in general to acoustic perception enhancement systems and in particular to a new and useful eyeglass frame with an electroacoustic combination particularly adapted for use by persons having high frequency hearing loss.
Hearing aids for the hard-of-hearing which are installed in an eyeglass frame and are generally referred to as hearing glasses, are known from and described in the U.S. Pat. Nos. 2,207.585 to Cox, U.S. Pat. No. 2,792.457 to Zappeloni, U.S. Pat. No. 4,409.585 to Tanaka, U.S. Pat. No. 1,820.357 to Lindstrom, Austrian Pat. Nos. 245.647 and 318.033; as well as in the German AS's 1,188.140; 2,105.535 and 2,236.968; and in the German OS's 2,330.073; 2,361.595; 2,337.078; 2,401.962 and 2,948.847. All these hearing glasses are equipped with high amplification, to make it possible for the hard-of-hearing to communicate with the world around them. The frequency response of the known hearing aids is evolved from the result of an audiometric measurement of the hearing loss, and the transmitted and amplified frequency range extends from the low to the high and highest frequencies. To avoid, to a large extent, an acoustic feedback between sound receiver and transducer, it is necessary not to allow the sound which is radiated into the inner ear, to get outside the ear. This is achieved, in general, by means of a plug which is tightly fitted in the ear canal. With such a tightly fitting plug natural hearing is not possible any more. In the patent of Cox either bone conduction devices or miniature headphones are mentioned, which, according to knowledge in 1936, are tightly fitting the ear. The lens, used as the pickup element, has a bi-directional sensitivity enhancing acoustic feedback between pickup and reproducer, which can be avoided only by a tightly fitting transducer plug. Lindstrom describes a device for blind people, with photocells in place of microphones, an arrangement that cannot create any feedback. All other above mentioned patents make use of ear plugs tightly fitted to the ear canal.
Now besides that group of persons whose hearing loss is so great that communication with them, without a hearing aid, is difficult if not impossible, there is also a very large group of mostly older persons whose hearing ability is quite sufficient for everday life but shows a certain inability to concentrate on sound from a specific direction. For such persons a conventional hearing aid does not help because present day hearing aids are not based on psychoacoustic considerations.
The majority of persons with only slight hearing deficiency can still hear most sounds but cannot concentrate on sound from a specific direction, especially under conditions where different sounds exist at the same time and originating from sources in different directions as happens during a cocktail party or speech in reveberant rooms or just any sound in a noisy surrounding as with street traffic, or in any concert hall or theater. Concentration on a specific sound from a specific direction in a soundfield with other sound coming from other directions, is only possible with natural hearing. Natural hearing requires transmission to the brain of interaural time and intensity differences as well as undistorted pinna transfer functions.
Present-day hearing aids as well as those covered by patents (see above) but not utilized, can not fulfill these requirements. This invention aims at bringing natural hearing undistorted and unimpeded to the brain.
All those hearing aids and patented designs have only one aim: to amplify. Most designs have facilities to adapt the amplification values at different frequencies to the deficiencies of the ear of the hard-of-hearing. E. W. Johnson, Dir. of Clinical Audiology for the Otologic Medical Group in Los Angeles, Calif. has conducted a study on 500 consecutive fittings of intracanal hearing aids, after having fitted such an aid to president Reagan. This study showed:
1. In order to correct not only the frequency-dependent level deficiencies, binaural fitting is necessary. PA1 2. Intra-canal aids create many problems: Of the 500 cases, 168 complained mainly about occlusion, but also about internal feedback, And 90 more could not use the hearing aids for reasons of inflammation etc. PA1 3. Audiometric measurements showed that 50% have the same hearing loss and same frequency response.
This study was reported in Audiological Acoustics, Vol. 24, No. 6, Dec. 1985, p. 158-188.